Methods for manufacturing and assembling dual material tissue interface for negative-pressure therapy

ABSTRACT

A dressing for treating tissue with negative pressure is provided herein comprising a composite of dressing layers, including a release film, a perforated coated polymer film, a manifold, and an adhesive cover. Additionally, a method of manufacturing the dressing may comprise applying a cross-linkable polymer to a polymer film, curing the cross-linkable polymer to a gel layer to form a coated polymer film, and perforating the coated polymer film to form fluid restrictions, such as slits and/or slots, though the coated polymer film.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/000,284, entitled “METHODS FOR MANUFACTURING AND ASSEMBLING DUALMATERIAL TISSUE INTERFACE FOR NEGATIVE-PRESSURE THERAPY,” filed Jun. 5,2018, which claims the benefit, under 35 U.S.C. § 119(e), of the filingof U.S. Provisional Patent Application Ser. No. 62/615,821, entitled“METHODS FOR MANUFACTURING AND ASSEMBLING DUAL MATERIAL TISSUE INTERFACEFOR NEGATIVE-PRESSURE THERAPY,” filed Jan. 10, 2018; U.S. ProvisionalPatent Application Ser. No. 62/613,494, entitled “PEEL AND PLACEDRESSING FOR THICK EXUDATE AND INSTILLATION,” filed Jan. 4, 2018; U.S.Provisional Patent Application Ser. No. 62/592,950, entitled“MULTI-LAYER WOUND FILLER FOR EXTENDED WEAR TIME,” filed Nov. 30, 2017;U.S. Provisional Patent Application Ser. No. 62/576,498, entitled“SYSTEMS, APPARATUSES, AND METHODS FOR NEGATIVE-PRESSURE TREATMENT WITHREDUCED TISSUE IN-GROWTH,” filed Oct. 24, 2017; U.S. Provisional PatentApplication Ser. No. 62/565,754, entitled “COMPOSITE DRESSINGS FORIMPROVED GRANULATION AND REDUCED MACERATION WITH NEGATIVE-PRESSURETREATMENT,” filed Sep. 29, 2017; U.S. Provisional Patent ApplicationSer. No. 62/516,540, entitled “TISSUE CONTACT INTERFACE,” filed Jun. 7,2017; U.S. Provisional Patent Application Ser. No. 62/516,550, entitled“COMPOSITE DRESSINGS FOR IMPROVED GRANULATION AND REDUCED MACERATIONWITH NEGATIVE-PRESSURE TREATMENT,” filed Jun. 7, 2017; and U.S.Provisional Patent Application Ser. No. 62/516,566, entitled “COMPOSITEDRESSINGS FOR IMPROVED GRANULATION AND REDUCED MACERATION WITHNEGATIVE-PRESSURE TREATMENT,” filed Jun. 7, 2017, all of which areincorporated herein by reference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally totissue treatment systems and more particularly, but without limitation,to methods of manufacturing a dual material tissue interface fornegative-pressure therapy.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds or other tissue with reduced pressure may becommonly referred to as “negative-pressure therapy,” but is also knownby other names, including “negative-pressure wound therapy,”“reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,”and “topical negative-pressure,” for example. Negative-pressure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

There is also widespread acceptance that cleansing a tissue site can behighly beneficial for new tissue growth. For example, a wound or acavity can be washed out with a stream of liquid solution fortherapeutic purposes. These practices are commonly referred to as“irrigation” and “lavage” respectively. “Instillation” is anotherpractice that generally refers to a process of slowly introducing fluidto a tissue site and leaving the fluid for a prescribed period of timebefore removing the fluid. For example, instillation of topicaltreatment solutions over a wound bed can be combined withnegative-pressure therapy to further promote wound healing by looseningsoluble contaminants in a wound bed and removing infectious material. Asa result, soluble bacterial burden can be decreased, contaminantsremoved, and the wound cleansed.

While the clinical benefits of negative-pressure therapy and/orinstillation therapy are widely known, improvements to therapy systems,components, and processes may benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for treating tissue ina negative-pressure therapy environment are set forth in the appendedclaims. Illustrative embodiments are also provided to enable a personskilled in the art to make and use the claimed subject matter.

For example, in some embodiments, a dressing for treating tissue may bea composite of dressing layers including a release film, a perforatedcoated polymer film, a manifold, and an adhesive cover. The manifold maybe reticulated foam in some examples, and may be relatively thin andhydrophobic to reduce the fluid hold capacity of the dressing. Themanifold may also be thin to reduce the dressing profile and increaseflexibility, which can enable it to conform to wound beds and othertissue sites under negative pressure. In some embodiments, theperforations on the coated polymer film may be fluid restrictions suchas slits or slots.

In additional embodiments, a method of manufacturing a dressing fornegative-pressure treatment may comprise applying a cross-linkablepolymer to a polymer film, curing the cross-linkable polymer to a gellayer on the polymer film to form a coated polymer film, and perforatingthe coated polymer film to form fluid restrictions such as slits orslots. A laser can be used to perforate the coated polymer film tocreate a plurality of slots, for example.

Objectives, advantages, and a preferred mode of making and using theclaimed subject matter may be understood best by reference to theaccompanying drawings in conjunction with the following detaileddescription of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example embodiment of atherapy system that can provide negative-pressure treatment andinstillation treatment in accordance with this specification;

FIG. 2 is a graph illustrating additional details of example pressurecontrol modes that may be associated with some embodiments of thetherapy system of FIG. 1 ;

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system of FIG. 1 ;

FIG. 4 is an assembly view of an example of a dressing that may beassociated with some embodiments of the therapy system of FIG. 1 ;

FIG. 5 is a cross-sectional view of an example of a coated polymer filmthat has been perforated that may be associated with some embodiments ofthe dressing of FIG. 4 ;

FIG. 6 is a schematic view of an example of a coated polymer filmillustrating additional details that may be associated with someembodiments of the dressing of FIG. 4 ;

FIG. 7 is a flow diagram illustrating an example method of manufacturingsome components of dressings that may be associated with the therapysystem of FIG. 1 .

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides informationthat enables a person skilled in the art to make and use the subjectmatter set forth in the appended claims, but may omit certain detailsalready well-known in the art. The following detailed description is,therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference tospatial relationships between various elements or to the spatialorientation of various elements depicted in the attached drawings. Ingeneral, such relationships or orientation assume a frame of referenceconsistent with or relative to a patient in a position to receivetreatment. However, as should be recognized by those skilled in the art,this frame of reference is merely a descriptive expedient rather than astrict prescription.

FIG. 1 is a simplified functional block diagram of an example embodimentof a therapy system 100 that can provide negative-pressure therapy withinstillation of topical treatment solutions to a tissue site inaccordance with this specification.

The term “tissue site” in this context broadly refers to a wound,defect, or other treatment target located on or within tissue,including, but not limited to, a surface wound, bone tissue, adiposetissue, muscle tissue, neural tissue, dermal tissue, vascular tissue,connective tissue, cartilage, tendons, or ligaments. A wound may includechronic, acute, traumatic, subacute, and dehisced wounds,partial-thickness burns, ulcers (such as diabetic, pressure, or venousinsufficiency ulcers), flaps, and grafts, for example. A surface wound,as used herein, is a wound on the surface of a body that is exposed tothe outer surface of the body, such as an injury or damage to theepidermis, dermis, and/or subcutaneous layers. Surface wounds mayinclude ulcers or closed incisions, for example. A surface wound, asused herein, does not include wounds within an intra-abdominal cavity.The term “tissue site” may also refer to areas of any tissue that arenot necessarily wounded or defective, but are instead areas in which itmay be desirable to add or promote the growth of additional tissue. Forexample, negative pressure may be applied to a tissue site to growadditional tissue that may be harvested and transplanted.

The therapy system 100 may include a source or supply of negativepressure, such as a negative-pressure source 105, a dressing 110, afluid container, such as a container 115, and a regulator or controller,such as a controller 120, for example. Additionally, the therapy system100 may include sensors to measure operating parameters and providefeedback signals to the controller 120 indicative of the operatingparameters. As illustrated in FIG. 1 , for example, the therapy system100 may include a first sensor 125 and a second sensor 130 coupled tothe controller 120. As illustrated in the example of FIG. 1 , thedressing 110 may comprise or consist essentially of a tissue interface135, a cover 140, or both in some embodiments.

The therapy system 100 may also include a source of instillationsolution. For example, a solution source 145 may be fluidly coupled tothe dressing 110, as illustrated in the example embodiment of FIG. 1 .The solution source 145 may be fluidly coupled to a positive-pressuresource such as the positive-pressure source 150, a negative-pressuresource such as the negative-pressure source 105, or both in someembodiments. A regulator, such as an instillation regulator 155, mayalso be fluidly coupled to the solution source 145 and the dressing 110to ensure proper dosage of instillation solution (e.g. saline) to atissue site. For example, the instillation regulator 155 may comprise apiston that can be pneumatically actuated by the negative-pressuresource 105 to draw instillation solution from the solution source duringa negative-pressure interval and to instill the solution to a dressingduring a venting interval. Additionally or alternatively, the controller120 may be coupled to the negative-pressure source 105, thepositive-pressure source 150, or both, to control dosage of instillationsolution to a tissue site. In some embodiments, the instillationregulator 155 may also be fluidly coupled to the negative-pressuresource 105 through the dressing 110, as illustrated in the example ofFIG. 1 .

Some components of the therapy system 100 may be housed within or usedin conjunction with other components, such as sensors, processing units,alarm indicators, memory, databases, software, display devices, or userinterfaces that further facilitate therapy. For example, in someembodiments, the negative-pressure source 105 may be combined with thesolution source 145, the controller 120, and other components into atherapy unit.

In general, components of the therapy system 100 may be coupled directlyor indirectly. For example, the negative-pressure source 105 may bedirectly coupled to the container 115 and may be indirectly coupled tothe dressing 110 through the container 115. Coupling may include fluid,mechanical, thermal, electrical, or chemical coupling (such as achemical bond), or some combination of coupling in some contexts. Forexample, the negative-pressure source 105 may be electrically coupled tothe controller 120 and fluidly coupled to one or more distributioncomponents to provide a fluid path to a tissue site. In someembodiments, components may also be coupled by virtue of physicalproximity, being integral to a single structure, or being formed fromthe same piece of material.

A distribution component is preferably detachable and may be disposable,reusable, or recyclable. The dressing 110 and the container 115 areillustrative of distribution components. A fluid conductor is anotherillustrative example of a distribution component. A “fluid conductor,”in this context, broadly includes a tube, pipe, hose, conduit, or otherstructure with one or more lumina or open pathways adapted to convey afluid between two ends. Typically, a tube is an elongated, cylindricalstructure with some flexibility, but the geometry and rigidity may vary.Moreover, some fluid conductors may be molded into or otherwiseintegrally combined with other components. Distribution components mayalso include or comprise interfaces or fluid ports to facilitatecoupling and de-coupling other components. In some embodiments, forexample, a dressing interface may facilitate coupling a fluid conductorto the dressing 110. For example, such a dressing interface may be aSENSAT.R.A.C.™ Pad available from Kinetic Concepts, Inc. of San Antonio,Tex.

A negative-pressure supply, such as the negative-pressure source 105,may be a reservoir of air at a negative pressure or may be a manual orelectrically-powered device. Examples of a suitable negative-pressuresupply may include a vacuum pump, a suction pump, a wall suction portavailable at many healthcare facilities, or a micro-pump. “Negativepressure” generally refers to a pressure less than a local ambientpressure, such as the ambient pressure in a local environment externalto a sealed therapeutic environment. In many cases, the local ambientpressure may also be the atmospheric pressure at which a tissue site islocated. Alternatively, the pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Unless otherwiseindicated, values of pressure stated herein are gauge pressures.References to increases in negative pressure typically refer to adecrease in absolute pressure, while decreases in negative pressuretypically refer to an increase in absolute pressure. While the amountand nature of negative pressure applied to a tissue site may varyaccording to therapeutic requirements, the pressure is generally a lowvacuum, also commonly referred to as a rough vacuum, between −5 mm Hg(−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges arebetween −50 mm Hg (−6.7 kPa) and −300 mm Hg (−39.9 kPa).

The container 115 is representative of a container, canister, pouch, orother storage component, which can be used to manage exudates and otherfluids withdrawn from a tissue site. In many environments, a rigidcontainer may be preferred or required for collecting, storing, anddisposing of fluids. In other environments, fluids may be properlydisposed of without rigid container storage, and a re-usable containercould reduce waste and costs associated with negative-pressure therapy.

A controller, such as the controller 120, may be a microprocessor orcomputer programmed to operate one or more components of the therapysystem 100, such as the negative-pressure source 105. In someembodiments, for example, the controller 120 may be a microcontroller,which generally comprises an integrated circuit containing a processorcore and a memory programmed to directly or indirectly control one ormore operating parameters of the therapy system 100. Operatingparameters may include the power applied to the negative-pressure source105, the pressure generated by the negative-pressure source 105, or thepressure distributed to the tissue interface 135, for example. Thecontroller 120 is also preferably configured to receive one or moreinput signals, such as a feedback signal, and programmed to modify oneor more operating parameters based on the input signals.

Sensors, such as the first sensor 125 and the second sensor 130, aregenerally known in the art as any apparatus operable to detect ormeasure a physical phenomenon or property, and generally provide asignal indicative of the phenomenon or property that is detected ormeasured. For example, the first sensor 125 and the second sensor 130may be configured to measure one or more operating parameters of thetherapy system 100. In some embodiments, the first sensor 125 may be atransducer configured to measure pressure in a pneumatic pathway andconvert the measurement to a signal indicative of the pressure measured.In some embodiments, for example, the first sensor 125 may be apiezo-resistive strain gauge. The second sensor 130 may optionallymeasure operating parameters of the negative-pressure source 105, suchas a voltage or current, in some embodiments. Preferably, the signalsfrom the first sensor 125 and the second sensor 130 are suitable as aninput signal to the controller 120, but some signal conditioning may beappropriate in some embodiments. For example, the signal may need to befiltered or amplified before it can be processed by the controller 120.Typically, the signal is an electrical signal, but may be represented inother forms, such as an optical signal.

The tissue interface 135 can be generally adapted to partially or fullycontact a tissue site. The tissue interface 135 may take many forms andmay have many sizes, shapes, or thicknesses, depending on a variety offactors, such as the type of treatment being implemented or the natureand size of a tissue site. For example, the size and shape of the tissueinterface 135 may be adapted to the contours of deep and irregularshaped tissue sites. Moreover, any or all of the surfaces of the tissueinterface 135 may have projections or an uneven, coarse, or jaggedprofile that can induce strains and stresses on a tissue site, which canpromote granulation at the tissue site.

In some embodiments, the tissue interface 135 may comprise or consistessentially of a manifold. A “manifold” in this context generallyincludes any substance or structure providing a plurality of pathwaysadapted to collect or distribute fluid across a tissue site underpressure. For example, a manifold may be adapted to receive negativepressure from a source and distribute negative pressure through multipleapertures across a tissue site, which may have the effect of collectingfluid from across a tissue site and drawing the fluid toward the source.In some embodiments, the fluid path may be reversed or a secondary fluidpath may be provided to facilitate delivering fluid, such as fluid froma source of instillation solution, across a tissue site.

In some illustrative embodiments, the pathways of a manifold may beinterconnected to improve distribution or collection of fluids across atissue site. In some illustrative embodiments, a manifold may be aporous foam material having interconnected cells or pores. For example,open-cell foam, porous tissue collections, and other porous materialsuch as gauze or felted mat generally include pores, edges, and/or wallsadapted to form interconnected fluid channels. Liquids, gels, and otherfoams may also include, or be cured to include, apertures and fluidpathways. In some embodiments, a manifold may additionally oralternatively comprise projections that form interconnected fluidpathways. For example, a manifold may be molded to provide surfaceprojections that define interconnected fluid pathways.

The average pore size of foam may vary according to needs of aprescribed therapy. For example, in some embodiments, the tissueinterface 135 may comprise or consist essentially of foam having poresizes in a range of 400-600 microns. The tensile strength of the tissueinterface 135 may also vary according to needs of a prescribed therapy.For example, the tensile strength of foam may be increased forinstillation of topical treatment solutions. In some examples, thetissue interface 135 may be reticulated polyurethane foam such as foundin GRANUFOAM™ dressing or V.A.C. VERAFLO™ dressing, both available fromKinetic Concepts, Inc. of San Antonio, Tex.

The tissue interface 135 may further promote granulation at a tissuesite when pressure within the sealed therapeutic environment is reduced.For example, any or all of the surfaces of the tissue interface 135 mayhave an uneven, coarse, or jagged profile that can induce microstrainsand stresses at a tissue site if negative pressure is applied throughthe tissue interface 135.

In some embodiments, the tissue interface 135 may be constructed frombioresorbable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include, withoutlimitation, polycarbonates, polyfumarates, and caprolactones. The tissueinterface 135 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with the tissue interface135 to promote cell-growth. A scaffold is generally a substance orstructure used to enhance or promote the growth of cells or formation oftissue, such as a three-dimensional porous structure that provides atemplate for cell growth. Illustrative examples of scaffold materialsinclude calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites,carbonates, or processed allograft materials.

In some embodiments, the cover 140 may provide a bacterial barrier andprotection from physical trauma. The cover 140 may also be constructedfrom a material that can reduce evaporative losses and provide a fluidseal between two components or two environments, such as between atherapeutic environment and a local external environment. The cover 140may comprise or consist of, for example, an elastomeric film or membranethat can provide a seal adequate to maintain a negative pressure at atissue site for a given negative-pressure source. The cover 140 may havea high moisture-vapor transmission rate (MVTR) in some applications. Forexample, the MVTR may be at least 450 grams per square meter pertwenty-four hours in some embodiments, measured using an upright cuptechnique according to ASTM E96/E96M Upright Cup Method at 38° C. and10% relative humidity (RH). In some embodiments, an MVTR up to 5,000grams per square meter per twenty-four hours may provide effectivebreathability and mechanical properties.

In some example embodiments, the cover 140 may be a polymer drape, suchas a polyurethane film, that is permeable to water vapor but impermeableto liquid. Such drapes typically have a thickness in the range of 25-50microns. For permeable materials, the permeability generally should below enough that a desired negative pressure may be maintained. Forexample, the cover 140 may comprise one or more of the followingmaterials: polyurethane (PU), such as hydrophilic polyurethane;cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinylpyrrolidone; hydrophilic acrylics; silicones, such as hydrophilicsilicone elastomers; natural rubbers; polyisoprene; styrene butadienerubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber;ethylene propylene rubber; ethylene propylene diene monomer;chlorosulfonated polyethylene; polysulfide rubber; ethylene vinylacetate (EVA); co-polyester; and polyether block polymide copolymers.Such materials are commercially available as, for example, Tegaderm®drape, commercially available from 3M Company, Minneapolis Minn.;polyurethane (PU) drape, commercially available from Avery DennisonCorporation, Pasadena, Calif.; polyether block polyamide copolymer(PEBAX), for example, from Arkema S.A., Colombes, France; and Inspire2301 and Inpsire 2327 polyurethane films, commercially available fromExpopack Advanced Coatings, Wrexham, United Kingdom. In someembodiments, the cover 140 may comprise INSPIRE 2301 having an MVTR(upright cup technique) of 2600 g/m²/24 hours and a thickness of about30 microns.

An attachment device may be used to attach the cover 140 to anattachment surface, such as undamaged epidermis, a gasket, or anothercover. The attachment device may take many forms. For example, anattachment device may be a medically-acceptable, pressure-sensitiveadhesive configured to bond the cover 140 to epidermis around a tissuesite. In some embodiments, for example, some or all of the cover 140 maybe coated with an adhesive, such as an acrylic adhesive, which may havea coating weight of 25-65 grams per square meter (g.s.m.). Thickeradhesives, or combinations of adhesives, may be applied in someembodiments to improve the seal and reduce leaks. Other exampleembodiments of an attachment device may include a double-sided tape,paste, hydrocolloid, hydrogel, silicone gel, or organogel.

The solution source 145 may also be representative of a container,canister, pouch, bag, or other storage component, which can provide asolution for instillation therapy. Compositions of solutions may varyaccording to a prescribed therapy, but examples of solutions that may besuitable for some prescriptions include hypochlorite-based solutions,silver nitrate (0.5%), sulfur-based solutions, biguanides, cationicsolutions, and isotonic solutions.

FIG. 2 is a graph illustrating additional details of an example controlmode that may be associated with some embodiments of the controller 120.In some embodiments, the controller 120 may have a continuous pressuremode, in which the negative-pressure source 105 is operated to provide aconstant target negative pressure, as indicated by line 205 and line210, for the duration of treatment or until manually deactivated.Additionally or alternatively, the controller may have an intermittentpressure mode, as illustrated in the example of FIG. 2 . In FIG. 2 , thex-axis represents time, and the y-axis represents negative pressuregenerated by the negative-pressure source 105 over time. In the exampleof FIG. 2 , the controller 120 can operate the negative-pressure source105 to cycle between a target pressure and atmospheric pressure. Forexample, the target pressure may be set at a value of 125 mmHg, asindicated by line 205, for a specified period of time (e.g., 5 min),followed by a specified period of time (e.g., 2 min) of deactivation, asindicated by the gap between the solid lines 215 and 220. The cycle canbe repeated by activating the negative-pressure source 105, as indicatedby line 220, which can form a square wave pattern between the targetpressure and atmospheric pressure.

In some example embodiments, the increase in negative-pressure fromambient pressure to the target pressure may not be instantaneous. Forexample, the negative-pressure source 105 and the dressing 110 may havean initial rise time, as indicated by the dashed line 225. The initialrise time may vary depending on the type of dressing and therapyequipment being used. For example, the initial rise time for one therapysystem may be in a range of about 20-30 mmHg/second and in a range ofabout 5-10 mmHg/second for another therapy system. If the therapy system100 is operating in an intermittent mode, the repeating rise time, asindicated by the solid line 220, may be a value substantially equal tothe initial rise time as indicated by the dashed line 225.

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system 100. In FIG. 3 , the x-axis represents time and they-axis represents negative pressure generated by the negative-pressuresource 105. The target pressure in the example of FIG. 3 can vary withtime in a dynamic pressure mode. For example, the target pressure mayvary in the form of a triangular waveform, varying between a negativepressure of 50 and 125 mmHg with a rise time 305 set at a rate of +25mmHg/min. and a descent time 310 set at −25 mmHg/min. In otherembodiments of the therapy system 100, the triangular waveform may varybetween negative pressure of 25 and 125 mmHg with a rise time 305 set ata rate of +30 mmHg/min and a descent time 310 set at −30 mmHg/min.

In some embodiments, the controller 120 may control or determine avariable target pressure in a dynamic pressure mode, and the variabletarget pressure may vary between a maximum and minimum pressure valuethat may be set as an input prescribed by an operator as the range ofdesired negative pressure. The variable target pressure may also beprocessed and controlled by the controller 120, which can vary thetarget pressure according to a predetermined waveform, such as atriangular waveform, a sine waveform, or a saw-tooth waveform. In someembodiments, the waveform may be set by an operator as the predeterminedor time-varying negative pressure desired for therapy.

FIG. 4 is an assembly view of an example of the dressing 110 of FIG. 1 ,illustrating additional details that may be associated with someembodiments in which the tissue interface 135 comprises more than onelayer. In the example of FIG. 4 , the tissue interface 135 comprises amanifold 405 and a coated polymer film 410. In some embodiments, themanifold 405 may be disposed in between the coated polymer film 410 andthe cover 140. The manifold 405 and/or the coated polymer film 410 mayalso be bonded to an adjacent layer in some embodiments.

The manifold 405 may comprise or consist essentially of a means forcollecting or distributing fluid across the tissue interface 135 underpressure. For example, the manifold 405 may be adapted to receivenegative pressure from a source and distribute negative pressure throughmultiple apertures across the tissue interface 135, which may have theeffect of collecting fluid from across a tissue site and drawing thefluid toward the source. In some embodiments, the fluid path may bereversed or a secondary fluid path may be provided to facilitatedelivering fluid, such as from a source of instillation solution, acrossthe tissue interface 135.

In some illustrative embodiments, the manifold 405 may comprise aplurality of pathways, which can be interconnected to improvedistribution or collection of fluids. In some embodiments, the manifold405 may comprise or consist essentially of a porous material havinginterconnected fluid pathways. For example, open-cell foam, poroustissue collections, and other porous material such as gauze or feltedmat generally include pores, edges, and/or walls adapted to forminterconnected fluid channels. Liquids, gels, and other foams may alsoinclude or be cured to include apertures and fluid pathways. In someembodiments, the manifold 405 may additionally or alternatively compriseprojections that form interconnected fluid pathways. For example, themanifold 405 may be molded to provide surface projections that defineinterconnected fluid pathways. Any or all of the surfaces of themanifold 405 may have an uneven, coarse, or jagged profile.

In some embodiments, the manifold 405 may comprise or consistessentially of reticulated foam having pore sizes and free volume thatmay vary according to needs of a prescribed therapy. For example,reticulated foam having a free volume of at least 90% may be suitablefor many therapy applications, and foam having an average pore size in arange of 400-600 microns (40-50 pores per inch) may be particularlysuitable for some types of therapy. The tensile strength of the manifold405 may also vary according to needs of a prescribed therapy. Forexample, the tensile strength of the manifold 405 may be increased forinstillation of topical treatment solutions. The 25% compression loaddeflection of the manifold 405 may be at least 0.35 pounds per squareinch, and the 65% compression load deflection may be at least 0.43pounds per square inch. In some embodiments, the tensile strength of themanifold 405 may be at least 10 pounds per square inch. The manifold 405may have a tear strength of at least 2.5 pounds per inch. In someembodiments, the manifold 405 may be foam comprised of polyols such aspolyester or polyether, isocyanate such as toluene diisocyanate, andpolymerization modifiers such as amines and tin compounds. In onenon-limiting example, the manifold 405 may be a reticulated polyurethaneether foam such as used in GRANUFOAM™ dressing or V.A.C. VERAFLO™dressing, both available from KCl of San Antonio, Tex.

The thickness of the manifold 405 may also vary according to needs of aprescribed therapy. For example, the thickness of the manifold 405 maybe decreased to relieve stress on other layers and to reduce tension onperipheral tissue. The thickness of the manifold 405 can also affect theconformability of the manifold 405. In some embodiments, a thickness ina range of about 5 millimeters to 10 millimeters may be suitable.

As illustrated in the example of FIG. 4 , the coated polymer film 410may have one or more fluid restrictions 420. The fluid restrictions 420can be distributed uniformly or randomly across the coated polymer film410. The fluid restrictions 420 may be bi-directional andpressure-responsive. For example, the fluid restrictions 420 cangenerally comprise or consist essentially of an elastic passage throughthe coated polymer film 410 that is normally unstrained to substantiallyreduce liquid flow, and the elastic passage can expand in response to apressure gradient. In some embodiments, the fluid restrictions 420 maycomprise or consist essentially of perforations in the coated polymerfilm 410. Perforations may be formed by removing material from thecoated polymer film 410. For example, perforations may be formed bycutting through the coated polymer film 410, which may also deform theedges of the perforations in some embodiments. In the absence of apressure gradient across the perforations, the passages may besufficiently small to form a seal or flow restriction, which cansubstantially reduce or prevent liquid flow. Additionally oralternatively, one or more of the fluid restrictions 420 may be anelastomeric valve that is normally closed when unstrained tosubstantially prevent liquid flow and can open in response to a pressuregradient. A fenestration in the coated polymer film 410 may be asuitable valve for some applications. Fenestrations may also be formedby removing material from the coated polymer film 410, but the amount ofmaterial removed and the resulting dimensions of the fenestrations maybe up to an order of magnitude less than perforations, and may notdeform the edges.

For example, some embodiments of the fluid restrictions 420 may compriseor consist essentially of one or more slots or combinations of slots inthe coated polymer film 410. In some examples, the fluid restrictions420 may comprise or consist of linear slots having a length less than 4millimeters and a width less than 1 millimeter. The length may be atleast 2 millimeters, and the width may be at least 0.4 millimeters insome embodiments. A length of about 3 millimeters and a width of about0.8 millimeter may be particularly suitable for many applications. Atolerance of about 0.1 millimeter may also be acceptable. Slots of suchconfigurations may function as imperfect valves that substantiallyreduce liquid flow in a normally closed or resting state. For example,such slots may form a flow restriction without being completely closedor sealed. The slots can expand or open wider in response to a pressuregradient to allow increased liquid flow.

In the example of FIG. 4 , the dressing 110 may further include anattachment mechanism, such as an adhesive 455. The adhesive 455 may be,for example, a medically-acceptable, pressure-sensitive adhesive thatextends about a periphery, a portion, or the entire cover 140. In someembodiments, for example, the adhesive 455 may be an acrylic adhesivehaving a coating weight between 25-65 grams per square meter (g.s.m.).Thicker adhesives, or combinations of adhesives, may be applied in someembodiments to improve the seal and reduce leaks. In some embodiments,such a layer of the adhesive 455 may be continuous or discontinuous.Discontinuities in the adhesive 455 may be provided by apertures orholes (not shown) in the adhesive 455. The apertures or holes in theadhesive 455 may be formed after application of the adhesive 455 or bycoating the adhesive 455 in patterns on a carrier layer, such as, forexample, a side of the cover 140. Apertures or holes in the adhesive 455may also be sized to enhance the moisture-vapor transfer rate of thedressing 110 in some example embodiments.

As illustrated in the example of FIG. 4 , in some embodiments, a releaseliner 460 may be attached to or positioned adjacent to the coatedpolymer film 410 to protect the adhesive 455 prior to use. The releaseliner 460 may also provide stiffness to assist with, for example,deployment of the dressing 110. Examples of the release liner 460 mayinclude a casting paper, a film, or polyethylene. Further, in someembodiments, the release liner 460 may be a polyester material such aspolyethylene terephthalate (PET), or similar polar semi-crystallinepolymer. The use of a polar semi-crystalline polymer for the releaseliner 460 may substantially preclude wrinkling or other deformation ofthe dressing 110. For example, the polar semi-crystalline polymer may behighly orientated and resistant to softening, swelling, or otherdeformation that may occur when brought into contact with components ofthe dressing 110 or when subjected to temperature or environmentalvariations, or sterilization. In some embodiments, the release liner 460may have a surface texture that may be imprinted on an adjacent layer,such as the coated polymer film 410. Further, a release agent may bedisposed on a side of the release liner 460 that is configured tocontact the coated polymer film 410. For example, the release agent maybe a silicone coating and may have a release factor suitable tofacilitate removal of the release liner 460 by hand and without damagingor deforming the dressing 110. In some embodiments, the release agentmay be a fluorocarbon or a fluorosilicone, for example. In otherembodiments, the release liner 460 may be uncoated or otherwise usedwithout a release agent.

FIG. 4 also illustrates one example of a fluid conductor 465 and adressing interface 470. As shown in the example of FIG. 4 , the fluidconductor 465 may be a flexible tube, which can be fluidly coupled onone end to the dressing interface 470. The dressing interface 470 may bean elbow connector, as shown in the example of FIG. 4 , which can beplaced over an aperture 475 in the cover 140 to provide a fluid pathbetween the fluid conductor 465 and the tissue interface 135.

FIG. 5 is a cross-sectional view illustrating additional details thatmay be associated with some examples of the coated polymer film 410. Inthe example of FIG. 5 , the coated polymer film 410 comprises a polymerfilm 505. The polymer film 505 has a first side 510 and a second side515. The coated polymer film 410 of FIG. 5 also comprises a gel layer520. The first and/or the second side of the polymer film 505 may have agel layer 520 present formed from curing a cross-linkable polymer toform the coated polymer film 410. In the example of FIG. 5 , the gellayer 520 can be seen on the first side 510 of the polymer film 505. Thefluid restrictions 420 extend through the polymer film 505 and the gellayer 520. Additionally, in other embodiments, a gel layer 520 can alsobe present on the second side 515 of the polymer film 505. The gel layer520 can be co-extensive with the polymer film 505 (e.g. a full coating),or the gel layer 520 may be partially extensive with the polymer film505 (e.g. a partial coating).

The coated polymer film 410 may comprise or consist essentially of ameans for controlling or managing fluid flow. The coated polymer film410 comprises the polymer film 505 and the gel layer 520 formed thereonby curing a cross-linkable polymer on the polymer film 505. In someembodiments, the polymer film 505 may comprise or consist essentially ofa liquid-impermeable, elastomeric polymer. The polymer film 505 may alsohave a smooth or matte surface texture in some embodiments. A glossy orshiny finish better or equal to a grade B3 according to the SPI (Societyof the Plastics Industry) standards may be particularly advantageous forsome applications. In some embodiments, variations in surface height maybe limited to acceptable tolerances. For example, the surface of thepolymer film 505 may have a substantially flat surface, with heightvariations limited to 0.2 millimeters over a centimeter.

In some embodiments, the polymer film 505 may be hydrophobic. Thehydrophobicity of the polymer film may vary, and may have a contactangle with water of at least ninety degrees in some embodiments. In someembodiments the polymer film 505 may have a contact angle with water ofno more than 150 degrees. For example, in some embodiments, the contactangle of the polymer film may be in a range of at least 90 degrees toabout 120 degrees or in a range of at least 120 degrees to 150 degrees.Water contact angles can be measured using any standard apparatus.Although manual goniometers can be used to visually approximate contactangles, contact angle measuring instruments can often include anintegrated system involving a level stage, liquid dropper such as asyringe, camera, and software designed to calculate contact angles moreaccurately and precisely, among other things. Non-limiting examples ofsuch integrated systems may include the FTÅ125, FTÅ200, FTÅ2000, andFTÅ4000 systems, all commercially available from First Ten Angstroms,Inc., of Portsmouth, Va., and the DTA25, DTA30, and DTA100 systems, allcommercially available from Kruss GmbH of Hamburg, Germany. Unlessotherwise specified, water contact angles herein are measured usingdeionized and distilled water on a level sample surface for a sessiledrop added from a height of no more than 5 cm in air at 20-25° C. and20-50% relative humidity. Contact angles reported herein representaverages of 5-9 measured values, discarding both the highest and lowestmeasured values. The hydrophobicity of the polymer film 505 may befurther enhanced with a hydrophobic coating of other materials, such assilicones and fluorocarbons, either as coated from a liquid orplasma-coated.

The polymer film 505 may also be suitable for welding to other layers,including the manifold 405. For example, the polymer film 505 may beadapted for welding to polyurethane foams using heat, radio frequency(RF) welding, or other methods to generate heat, such as ultrasonicwelding. RF welding may be particularly suitable for more polarmaterials, such as polyurethane, polyamides, polyesters and acrylates.Sacrificial polar interfaces may be used to facilitate RF welding ofless polar film materials, such as polyethylene.

The area density of the polymer film 505 may vary according to aprescribed therapy or application. In some embodiments, an area densityof less than 40 grams per square meter may be suitable, and an areadensity of about 20-30 grams per square meter may be particularlyadvantageous for some applications.

In some embodiments, for example, the polymer film 505 may comprise orconsist essentially of a hydrophobic polymer, such as a polyethylenefilm. The simple and inert structure of polyethylene can provide asurface that interacts little, if at all, with biological tissues andfluids. Such a surface may encourage the free flow of liquid and lowadherence, which can be particularly advantageous for many applications.More polar films suitable for laminating to a polyethylene film includepolyamide, co-polyesters, ionomers, and acrylics. To aid in the bondbetween a polyethylene and polar film, tie layers may be used, such asethylene vinyl acetate or modified polyurethanes. An ethyl methylacrylate (EMA) film may also have suitable hydrophobic and weldingproperties for some configurations.

The gel layer 520 may comprise or consist essentially of a fixationlayer having a tacky surface and may be formed from curing a polymersuitable for providing a fluid seal with a tissue site. In certainembodiments, the gel layer 520 may have a peel adhesion of about 0.1N/2.5 cm to about 2.0 N/2.5 cm. Furthermore, the gel layer 520 may havea coating weight of about 100 g.s.m., and may have a substantially flatsurface in some examples. In some embodiments, the gel layer 520 mayhave a thickness of about 30 microns (μm) to about 100 microns (μm).Additionally, in some embodiments, the gel layer 520 may have a hardnessof about 5 Shore OO to about 80 Shore OO. The gel layer 520 may becomprised of hydrophobic or hydrophilic materials. For example, the gellayer 520 may comprise, without limitation, a silicone gel, ahydrocolloid, a hydrogel, a polyurethane gel, a polyolefin gel, ahydrogenated styrenic copolymer gel, or a foamed gel.

FIG. 6 is a schematic view of an example of the coated polymer film 410,illustrating additional details that may be associated with someembodiments. The gel layer 520 is not shown. The fluid restrictions 420may each consist essentially of one or more linear slots having a lengthof about 3 millimeters. FIG. 6 additionally illustrates an example of auniform distribution pattern of the fluid restrictions 420. In FIG. 6 ,the fluid restrictions 420 are substantially coextensive with the coatedpolymer film 410 and are distributed across the coated polymer film 410in a grid of parallel rows and columns, in which the slots are alsomutually parallel to each other. In some embodiments, the rows may bespaced about 3 millimeters on center, and the fluid restrictions 420within each of the rows may be spaced about 3 millimeters on center, asillustrated in the example of FIG. 5 . The fluid restrictions 420 inadjacent rows may be aligned or offset. For example, adjacent rows maybe offset, as illustrated in FIG. 6 , so that the fluid restrictions 420are aligned in alternating rows and separated by about 6 millimeters.The spacing of the fluid restrictions 420 may vary in some embodimentsto increase the density of the fluid restrictions 420 according totherapeutic requirements.

In further embodiments, methods of manufacturing the dressings describedherein are also provided. In some embodiments, a method of manufacturinga dressing for negative-pressure treatment may comprise applying across-linkable polymer to the polymer film 505, curing thecross-linkable polymer to a gel layer 520 on the polymer film 505 toform the coated polymer film 410, and then perforating the coatedpolymer film 410 to form fluid restrictions 420 as discussed herein.

Examples of suitable cross-linkable polymers that can be applied to thepolymer film 505 include silicone; polyurethane; a thermoplasticelastomer, such as styrene ethylene butadiene styrene (SEBS); asuperabsorbent polymer, such as polyacrylic acid,2-acrylamido-2-methylpropan sulfonic acid (AMPS); and a hydrocolloid(superabsorbent particles such as carboxymethyl cellulose salts mixedinto soft rubber matrices (non-limiting examples include polyisoprene,or polybutadiene, or polyisobutylene, or mixtures or copolymers of thesame). In a particular embodiment silicone is applied to the polymerfilm 505. Many suitable commercial silicone grades are available, forexample, DOW 9700 and DOW 9177 from the Dow Corning Chemical Company ofMidland, Mich. Alternatively, a hydrocolloid can be applied to thepolymer film 505. Suitable grades of hydrocolloids are available, forexample part number 110008 from Amparo Medical Technologies, Inc. ofPlacentia, Calif.

The cross-linkable polymer can be applied to the polymer film 505 by anysuitable technique. For example, the cross-linkable polymer may beapplied to the polymer film 505 by laminating, rolling such as a “knifeover roll” technique, dipping, transferring or spraying thecross-linkable polymer on the polymer film 505.

In some embodiments, the cross-linkable polymer is only applied to thefirst side 510 of the polymer film 505. Alternatively, in otherembodiments the cross-linkable polymer is applied to both the first side510 and the second side 515 of the polymer film 505. When thecross-linkable polymer is applied to the second side 515 of the polymerfilm 505 it may be used as an adhesive to adhere or bond the polymerfilm 505 to the manifold 405. In some embodiments, the cross-linkablepolymer can be applied to both the first side 510 and the second side515 of the polymer film 505 prior to bonding the polymer film 505 to themanifold 405. Subsequently, the cross-linkable polymer on the first side510 of the polymer film 505 can be cured. Alternatively, thecross-linkable polymer can be applied to the first side 510 of thepolymer film, cured to a gel layer 520, and then the cross-linkablepolymer can be applied to the second side 515 of the polymer film 505and bonded to the manifold 405.

The cross-linkable polymer can be cured to form the gel layer 520 on thepolymer film 505 to form the coated polymer film 410. Examples ofsuitable curing techniques include, but are not limited to, a heat cure,an ionizing radiation cure (such as ultraviolet light, gamma rays,x-rays, and e-beam), an addition cure, a free radical cure, acondensation cure or a combination thereof. In a particular embodiment,the curing step is performed by an addition cure. An addition cure isknown in the art and is commonly available by mixing a two-part mix of(1) a source polymer, such as long chains of polydimethylsiloxane; and(2) a catalyst, such as platinum. However, rhodium, tin or titaniumcatalysts can also be used. Alternatively, a free radical cure could beused for the curing step, such as a peroxide cure. Additionally, if thecross-linkable polymer is a transfer gel, it can be applied to thepolymer film 505 and further cured to the appropriate tack or peeladhesion level.

The coated polymer film 410 is perforated by any suitable technique toform fluid restrictions 420 through the coated polymer film 410. Thisincludes the polymer film 505 and the gel layer 520. As discussedherein, suitable techniques include laser, knife, heat or other meansfor perforating; and the perforating step can create fluid restrictions,such as slits and/or slots through the coated polymer film 410. Theslits and/or slots can take many patterns and be of certain lengths andwidths as discussed previously. Additionally or alternatively, the fluidrestrictions may comprise or consist essentially of elastomeric valves,preferably fenestrations, that are normally closed.

In some embodiments, perforating may occur after curing thecross-linkable polymer, but prior to bonding the polymer film 505 or thecoated polymer film 410 to the manifold 405. Alternatively, in otherembodiments perforating may occur after the polymer film 505 or thecoated polymer film 410 is bonded to the manifold 405.

In additional embodiments, one or more of the components of the dressing110 may be treated with an antimicrobial agent. For example, themanifold 405 may be a foam, mesh, or non-woven coated with anantimicrobial agent. In some embodiments, the manifold 405 may compriseantimicrobial elements, such as fibers coated with an antimicrobialagent. Additionally or alternatively, some embodiments of the polymerfilm 410 may be a polymer coated or mixed with an antimicrobial agent.In other examples, the fluid conductor 465 may additionally oralternatively be treated with one or more antimicrobial agents. Suitableantimicrobial agents may include, for example, metallic silver, PHMB,iodine or its complexes and mixes such as povidone iodine, copper metalcompounds, chlorhexidine, or some combination of these materials.

FIG. 7 is a flow diagram illustrating an example method 700 ofmanufacturing some components of the dressing 110. In the example ofFIG. 7 , a cross-linkable polymer can be applied to the polymer film 505at 705. The cross-linkable polymer can be cured to a gel layer 520 onthe polymer film to form a coated polymer film 410 at 715. For example,ultraviolet light, heat or an addition cure can be used to cure thecross-linkable polymer to a gel layer 520 to form the coated polymerfilm 410. The coated polymer film 410 can then be perforated at 720. Forexample, slots and/or slits may be formed through the coated polymerfilm 410 by a laser or other suitable means.

Individual components of the dressing 110 may be bonded or otherwisesecured to one another with a solvent or non-solvent adhesive or withthermal welding, for example, without adversely affecting fluidmanagement.

The manifold 405, the coated polymer film 410, the cover 140, or variouscombinations may be assembled before application or in situ. Forexample, the cover 140 may be laminated to the manifold 405, and thecoated polymer film 410 may be laminated to the manifold 405 oppositethe cover 140 in some embodiments. In some embodiments, one or morelayers of the tissue interface 135 may be coextensive. For example, themanifold 405 may be coextensive with the coated polymer film 410, asillustrated in the embodiment of FIG. 4 . In some embodiments, thedressing 110 may be provided as a single, composite dressing.

In use, the release liner 460 (if included) may be removed to expose thegel layer 520 of the coated polymer film 410, which may be placedwithin, over, on, or otherwise proximate to a tissue site, particularlya surface tissue site and adjacent epidermis. The coated polymer film410 may be interposed between the manifold 405 and a tissue site, whichcan substantially reduce or eliminate adverse interaction with themanifold 405. For example, the coated polymer film 410 may be placedover a surface wound (including edges of the wound) and undamagedepidermis to prevent direct contact with the manifold 405. Treatment ofa surface wound, or placement of the dressing 110 on a surface wound,includes placing the dressing 110 immediately adjacent to the surface ofthe body or extending over at least a portion of the surface of thebody. Treatment of a surface wound does not include placing the dressing110 wholly within the body or wholly under the surface of the body, suchas placing a dressing within an abdominal cavity. In some applications,at least some portion of the coated polymer film 410, the fluidrestrictions 420, or both may be exposed to a tissue site through thegel layer 520. The gel layer 520 may be sufficiently tacky to hold thedressing 110 in position, while also allowing the dressing 110 to beremoved or re-positioned without trauma to a tissue site.

Removing the release liner 460 can also expose the adhesive 455, and thecover 140 may be attached to an attachment surface. For example, thecover 140 may be attached to epidermis peripheral to a tissue site,around the manifold 405 and the coated polymer film 410.

Once the dressing 110 is in a desired position, the adhesive 455 may bepressed to bond the dressing 110 to the attachment surface. In someembodiments, the bond strength of the adhesive 455 may vary in differentlocations of the dressing 110.

The geometry and dimensions of the tissue interface 135, the cover 140,or both may vary to suit a particular application or anatomy. Forexample, the geometry or dimensions of the tissue interface 135 and thecover 140 may be adapted to provide an effective and reliable sealagainst challenging anatomical surfaces, such as an elbow or heel, atand around a tissue site.

Further, the dressing 110 may permit re-application or re-positioning toreduce or eliminate leaks, which can be caused by creases and otherdiscontinuities in the dressing 110 and a tissue site. The ability torectify leaks may increase the reliability of the therapy and reducepower consumption in some embodiments.

If not already configured, the dressing interface 470 may disposed overthe aperture 475 and attached to the cover 140. The fluid conductor 465may be fluidly coupled to the dressing interface 470 and to thenegative-pressure source 105.

In operation, the dressing 110 can provide a sealed therapeuticenvironment proximate to a tissue site, substantially isolated from theexternal environment, and the negative-pressure source 105 can reducepressure in the sealed therapeutic environment.

The fluid mechanics of using a negative-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to negative-pressuretherapy and instillation are generally well-known to those skilled inthe art, and the process of reducing pressure may be describedillustratively herein as “delivering,” “distributing,” or “generating”negative pressure, for example.

In general, exudate and other fluid flow toward lower pressure along afluid path. Thus, the term “downstream” typically implies something in afluid path relatively closer to a source of negative pressure or furtheraway from a source of positive pressure. Conversely, the term “upstream”implies something relatively further away from a source of negativepressure or closer to a source of positive pressure. Similarly, it maybe convenient to describe certain features in terms of fluid “inlet” or“outlet” in such a frame of reference. This orientation is generallypresumed for purposes of describing various features and componentsherein. However, the fluid path may also be reversed in someapplications, such as by substituting a positive-pressure source for anegative-pressure source, and this descriptive convention should not beconstrued as a limiting convention.

Negative pressure applied across the tissue site through the tissueinterface 135 in the sealed therapeutic environment can inducemacro-strain and micro-strain in the tissue site. Negative pressure canalso remove exudate and other fluid from a tissue site, which can becollected in container 115.

Negative pressure applied through the tissue interface 135 can create anegative pressure differential across the fluid restrictions 420 in thecoated polymer film 410, which can open or expand the fluid restrictions420 from their resting state. For example, in some embodiments in whichthe fluid restrictions 420 may comprise substantially closedfenestrations through the coated polymer film 410, a pressure gradientacross the fenestrations can strain the adjacent material of the coatedpolymer film 410 and increase the dimensions of the fenestrations toallow liquid movement through them, similar to the operation of aduckbill valve. Opening the fluid restrictions 420 can allow exudate andother liquid movement through the fluid restrictions 420 into themanifold 405 and the container 115. Changes in pressure can also causethe manifold 405 to expand and contract, and the interior border 450 mayprotect the epidermis from irritation. The coated polymer film 410 canalso substantially reduce or prevent exposure of tissue to the manifold405, which can inhibit growth of tissue into the manifold 405.

In some embodiments, the manifold 405 may be hydrophobic to minimizeretention or storage of liquid in the dressing 110. In otherembodiments, the manifold 405 may be hydrophilic. In an example in whichthe manifold 405 may be hydrophilic, the manifold 405 may also wickfluid away from a tissue site, while continuing to distribute negativepressure to the tissue site. The wicking properties of the manifold 405may draw fluid away from a tissue site by capillary flow or otherwicking mechanisms, for example. An example of a hydrophilic materialsuitable for some embodiments of the manifold 405 is a polyvinylalcohol, open-cell foam such as V.A.C. WHITEFOAM™ dressing availablefrom KCl of San Antonio, Tex. Other hydrophilic foams may include thosemade from polyether. Other foams that may exhibit hydrophiliccharacteristics include hydrophobic foams that have been treated orcoated to provide hydrophilicity.

If the negative-pressure source 105 is removed or turned-off, thepressure differential across the fluid restrictions 420 can dissipate,allowing the fluid restrictions 420 to move to their resting state andprevent or reduce the rate at which exudate or other liquid fromreturning to the tissue site through the coated polymer film 410.

In some applications, a filler may also be disposed between a tissuesite and the coated polymer film 410. For example, if the tissue site isa surface wound, a wound filler may be applied interior to theperiwound, and the coated polymer film 410 may be disposed over theperiwound and the wound filler. In some embodiments, the filler may be amanifold, such as open-cell foam. The filler may comprise or consistessentially of the same material as the manifold 405 in someembodiments.

Additionally or alternatively, instillation solution or other fluid maybe distributed to the dressing 110, which can increase the pressure inthe tissue interface 135. The increased pressure in the tissue interface135 can create a positive pressure differential across the fluidrestrictions 420 in the coated polymer film 410, which can open orexpand the fluid restrictions 420 from their resting state to allow theinstillation solution or other fluid to be distributed to a tissue site.

In some embodiments, the controller 120 may receive and process datafrom one or more sensors, such as the first sensor 125. The controller120 may also control the operation of one or more components of thetherapy system 100 to manage the pressure delivered to the tissueinterface 135. In some embodiments, controller 120 may include an inputfor receiving a desired target pressure and may be programmed forprocessing data relating to the setting and inputting of the targetpressure to be applied to the tissue interface 135. In some exampleembodiments, the target pressure may be a fixed pressure value set by anoperator as the target negative pressure desired for therapy at a tissuesite and then provided as input to the controller 120. The targetpressure may vary from tissue site to tissue site based on the type oftissue forming a tissue site, the type of injury or wound (if any), themedical condition of the patient, and the preference of the attendingphysician. After selecting a desired target pressure, the controller 120can operate the negative-pressure source 105 in one or more controlmodes based on the target pressure and may receive feedback from one ormore sensors to maintain the target pressure at the tissue interface135.

The systems, apparatuses, and methods described herein may providesignificant advantages over prior art. For example, some dressings fornegative-pressure therapy can require time and skill to be properlysized and applied to achieve a good fit and seal. In contrast, someembodiments of the dressing 110 can provide a negative-pressure dressingthat is simple to apply, reducing the time to apply and remove. In someembodiments, for example, the dressing 110 may be a fully-integratednegative-pressure therapy dressing that can be applied to a tissue site(including on the periwound) in one step, without being cut to size,while still providing or improving many benefits of othernegative-pressure therapy dressings that require sizing. Such benefitsmay include good manifolding, beneficial granulation, protection of theperipheral tissue from maceration, and a low-trauma and high-seal bond.These characteristics may be particularly advantageous for surfacewounds having moderate depth and medium-to-high levels of exudate. Thedressing 110 can also be manufactured with automated processes with highthroughput, which can lower part costs. Some embodiments of the dressing110 may remain on a tissue site for at least 5 days, and someembodiments may remain for at least 7 days. Antimicrobial agents in thedressing 110 may extend the usable life of the dressing 110 by reducingor eliminating infection risks that may be associated with extended use,particularly use with infected or highly exuding wounds.

While shown in a few illustrative embodiments, a person having ordinaryskill in the art will recognize that the systems, apparatuses, andmethods described herein are susceptible to various changes andmodifications that fall within the scope of the appended claims.Moreover, descriptions of various alternatives using terms such as “or”do not require mutual exclusivity unless clearly required by thecontext, and the indefinite articles “a” or “an” do not limit thesubject to a single instance unless clearly required by the context.Components may be also be combined or eliminated in variousconfigurations for purposes of sale, manufacture, assembly, or use. Forexample, in some configurations the dressing 110, the container 115, orboth may be eliminated or separated from other components formanufacture or sale. In other example configurations, the controller 120may also be manufactured, configured, assembled, or sold independentlyof other components.

The appended claims set forth novel and inventive aspects of the subjectmatter described above, but the claims may also encompass additionalsubject matter not specifically recited in detail. For example, certainfeatures, elements, or aspects may be omitted from the claims if notnecessary to distinguish the novel and inventive features from what isalready known to a person having ordinary skill in the art. Features,elements, and aspects described in the context of some embodiments mayalso be omitted, combined, or replaced by alternative features servingthe same, equivalent, or similar purpose without departing from thescope of the invention defined by the appended claims.

What is claimed is:
 1. A dressing for treating a tissue site,comprising: a coated polymer film comprising a polymer film having afirst side and a second side, a gel layer coupled to the first side ofthe polymer film and configured to be adjacent the tissue site, and aplurality of perforations configured to extend through the polymer filmand the gel layer, the plurality of perforations configured to expand inresponse to a negative pressure applied to the coated polymer film toallow liquid flow; a manifold configured to be positioned adjacent thecoated polymer film; and a sealing layer configured to cover themanifold; wherein the polymer film and the gel layer are hydrophobic. 2.The dressing of claim 1, wherein the gel layer is a first gel layer andthe coated polymer film further comprises a second gel layer coupled tothe second side of the polymer film.
 3. The dressing of claim 1, whereinthe gel layer is configured to be coextensive with the polymer film. 4.The dressing of claim 1, wherein the gel layer has a thickness of about30 μm to about 100 μm.
 5. The dressing of claim 1, wherein the gel layerhas a peel adhesion of about 0.1 N/2.5 cm to about 2.0 N/2.5 cm.
 6. Thedressing of claim 1, wherein the gel layer is formed from across-linkable polymer.
 7. The dressing of claim 1, wherein theplurality of perforations comprise a plurality of fluid restrictions. 8.The dressing of claim 1, wherein the plurality of perforations comprisea plurality of slits.
 9. The dressing of claim 8, wherein the pluralityof slits have a length less than about 4 millimeters and a width lessthan about 1 millimeters.
 10. The dressing of claim 8, wherein theplurality of slits have a length less than about 2 millimeters and awidth less than about 0.4 millimeters.
 11. The dressing of claim 8,wherein the plurality of slits have a length of about 3 millimeters andwidth of about 0.8 millimeters.
 12. The dressing of claim 1, wherein theplurality of perforations are distributed in a uniform pattern, theuniform pattern comprising a grid of parallel rows and columns.
 13. Thedressing of claim 1, wherein: the plurality of perforations aredistributed in parallel rows and columns; the rows are spaced about 3millimeters on center; and the plurality of perforations in each of therows are spaced about 3 millimeters on center.
 14. The dressing of claim1, wherein the plurality of perforations in adjacent rows are offset.15. The dressing of claim 1, wherein the plurality of perforationscomprise elastomeric valves that are normally closed.
 16. The dressingof claim 1, wherein the manifold comprises reticulated foam.
 17. Thedressing of claim 16, wherein the foam is porous and has a free volumeof at least 90%, and wherein the foam has an average pore size in arange of 400-600 μm.
 18. The dressing of claim 1, wherein the manifoldhas a thickness less than 7 mm.
 19. The dressing of claim 1, furthercomprising an adhesive configured to be coupled to at least a portion ofa tissue-facing side of the sealing layer; and a release layerconfigured to be positioned adjacent the coated polymer film andremovably coupled to the adhesive.